Some embodiments of the present invention relates generally to monolithic techniques for micromachined technologies and integrated circuits. More particularly, some embodiments of the present invention provide a method and resulting device including both MEMS and integrated circuits using standard IC foundry-compatible processes. Merely by way of example, embodiments of the invention can be applied to resonators, oscillators, RF filters, sensors, and the like.
Micromachined resonators and filters have been proposed to replace conventional frequency devices such as a quartz crystal and a film bulk acoustic resonator, commonly called FBARs. Quartz crystals have been used for decades for providing a clock signal for small watches, computers, and almost any electronic or cellular phone application. Although successful, quartz crystals have limitations. That is, quartz crystal technology is often packaged in cumbersome enclosures, which lead to large form factors and the like, for conventional microelectronic applications. Quartz crystals are also limited to a single frequency, which also limits its applications and efficiency.
To overcome the limitations of crystals and FBAR devices, MEMS resonators and filters have been proposed. MEMS resonators are often fabricated in a similar way as integrated circuit (IC) chips and have significant reduction in form factor. In addition, MEMS resonators have superior performance, e.g. high Q factor, lower power, and lower cost comparing to the conventional counterparts. Furthermore, multiple frequency MEMS filters can be integrated on a single chip. Although somewhat successful, MEMS resonators and filters have drawbacks and limited penetration.
As an example, conventional MEMS resonator technologies are often based on MEMS fabrication processes such as bulk and surface micromachining techniques. Such bulk and surface micromachining techniques generally limit the level of integration of MEMS with other types of conventional devices. Additionally, conventional bulk surface and micromachining techniques are often expensive and difficult to scale up for true high volume production. These and other limitations may be described throughout the present specification and more particularly below.
Thus, it is desirable to improve MEMS resonators.
Moreover, as described below, it is desirable to have improved devices and methods in other monolithic techniques for micromachined technologies and integrated circuits. Some examples of these techniques can be used for improving MEMS device including pressure sensors, the stability of timing circuits, RF circuits, and the like, microneedle technology, as well as improved battery anode materials.